Measurements of open circuit potential and electrochemical impedance spectroscopy (EIS) at open circuit condition have been employed to characterize the behaviour of the mechanically polished bismuth surface in hydrochloric acid solution of various concentrations (0.01–1.0 M). The air-formed (pre-immersion) bismuth oxide grows on the surface in all the test solutions, but its thickness decreases as the HCl concentration increases. The impedance results showed that bismuth surface reactivity towards oxide thickening decreases as chloride ions concentration increases as a result of their aggressiveness nature. The equivalent circuit model for fitting the spectra of the EIS data of bismuth in HCl solution indicated that the mechanism of Bi corrosion is controlled by the charge-transfer and diffusion processes. The mechanically polished bismuth surface was examined by scanning electron microscopy before and after immersion in 0.023 M HCl solution. The scanning electron micrographs have shown that the flawed regions formed on the mechanically polished Bi surface were repaired after immersion in the acid solution due to thickening of the oxide film.

中文翻译：

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铋在 HCl 溶液中的电化学行为

开路电位和电化学阻抗谱 (EIS) 在开路条件下的测量已被用来表征机械抛光的铋表面在各种浓度 (0.01-1.0 M) 的盐酸溶液中的行为。空气形成（预浸）氧化铋在所有测试溶液的表面上生长，但其厚度随着 HCl 浓度的增加而减小。阻抗结果表明铋表面对氧化物增稠的反应性随着氯离子浓度的增加而降低，这是由于它们的侵蚀性。用于拟合 HCl 溶液中铋的 EIS 数据光谱的等效电路模型表明，Bi 腐蚀的机制是由电荷转移和扩散过程控制的。在浸入 0.023 M HCl 溶液之前和之后，通过扫描电子显微镜检查机械抛光的铋表面。扫描电子显微照片表明，由于氧化膜增厚，在酸溶液中浸泡后，在机械抛光的 Bi 表面上形成的缺陷区域得到了修复。